This proposal relates to the feasibility of superovulating 40-50 eggs from the prepubertal female Syrian hamster (SH) as a cost effective source of quality-assured cryopreserved hamster eggs to service the needs of research and diagnostic laboratories engaged in human male fertility and future generation risk assessments. The desired endpoint, namely, favorable cryogenics and retention of fertilizability/sperm penetrability following thawing, will center upon the adaptation of the normal-like 78 hour PMS-hCG time interval to encourage synchronous nuclear and cytoplasmic maturation. The latter relationship was found to be essential for assessing maternal chromosome non-disjunction in the Chinese hamster (CH), in response to tubulin-interacting properties of test compounds. In the adult female CH, this vital consideration was satisfied by scheduling PMS and hCG in concert with the corresponding endogeneous surges of follicle-stimulating (FSH) and luteinizing (LH) hormones. When the 78 hour PMS-hCG time interval was applied to prepubertal CH and SH, optimal superovulation was readily, and predictably, attained. Preliminary evaluations suggest that this procedure may readily compensate for the residual immaturity of superovulated eggs derived with time intervals of 48-56 hours. Phase I activities will center upon: (a) clarifying age, weight, and hormonal dose relationships of 30-35 day old female SH; (b) assembling the in vitro fertilization/sperm penetration assays to begin gaining the necessary proficiencies to assess cryogenic procedures in relation to the performance of frozen-thawed eggs, particularly during Phase II, and (c) recognizing steps (or components) of the current manually-operated procedures for cryopreserving hamster eggs for possible adaptation and automation. Comparative studies will be limited to eggs superovulated with the 56 vs. 78 hour PMS-hCG time intervals, following simultaneous harvesting, cryopreserving, and thawing.